Some hybrid electric vehicles (HEVs) include both an electric motor and an internal combustion engine. The electric motor is typically coupled to a crankshaft of the engine via a flywheel, such as a dual-mass flywheel. The engine combusts an air/fuel mixture to generate drive torque that is transferred to the electric motor. In some implementations, the electric motor is further configured to be driven (e.g., by a battery system) to act as a dampener to vibrational disturbances to the crankshaft. Misfires of the engine are typically detected based on a crankshaft speed signal.
These sources of vibrational responses (the dual-mass flywheel, the electric motor dampening, an overall soft stiffness design of connections between the engine and other components, etc.), however, often cause a smaller separation or distinction in the crankshaft speed signal between normal and misfire events. Thus, engine misfire detection could be negatively affected with such an arrangement. Accordingly, while such misfire detection systems work for their intended purpose, there remains a need for improvement in the relevant art.